During this reporting period, studies on this project have concentrated on defining differences in surface exposure of a particular outer membrane protein--protein I--of gonococci (Gc). This protein's subunit size correlates with the organism's susceptibility to killing by normal human sera and the organism's ability to cause disseminated Gc infection. The findings reveal a marked difference in the manner in which protein I (P.I.) of serum-resistant Gc is disposed in the outer membrane in comparison with P.I. of serum-sensitive Gc. Attempts are underway to define the surface-exposed portions of these P.I. subunits through generation of monoclonal antibodies; development of monoclonal reagents directed against additional outer membrane proteins (P.II, P.III) and against both common and unique portions of pilus-subunit molecules (pilin).